i paid about $195 for a 0-5 watts us fm transmitter with a 1/4 wave antenna. after hooking up my laptop, dj mixer/mic i range 3-5 miles of coverage with the antenna being 30feet. then i connected a bnc to f type adapter to an ex radio station’s 1/4 antenna (70feet) and my range was 8 – 10 miles. to bad i can’t stay on the air!!!! really: should this be as if i am using a multiple (3) transmitter set up broadcasting from my main (master) transmitter. (1) part 15 us transmitter/antenna sold in a set (30ft pole) covering a 3-6 mile city. verses a (3) part 15 us transmitters covering a 8-10 mile city. FCC NEED TO UPDATE, GRANT PART 15 US TRANSMITTER COVERAGE 1-6 MILES!!!!!!!!!!!!
RE: us part 15 (FM) transmitter coverage range
47 CFR §15.239 covers the permissible use of the FM broadcast band by unlicensed operators subject to FCC rules.
In short, only about 11.43 nanowatts (0.000 000 011 43 watts) radiated by a center-fed 1/2-wave dipole will produce the legal field limit permitted for such unlicensed operators/systems.
Such a system can produce a useful signal to a typical, indoor, consumer-level FM receiver for only a few hundred feet — far less than 3-5 miles.
Just to note that the ~reliable reception range for FCC-licensed LPFM broadcast stations in the US radiating 100 watts from an antenna height about 100 feet above level/average terrain is on the order of 3 to 5 miles.
As a “heads up,” the FCC has issued citations to unlicensed operators radiating less power even than 50 milliwatts (0.05 watts).